Negative Effect Of Density Research Articles

Value implications of followers in social marketplaces: insights into ego network structures

PurposeIn social marketplaces, follower ego networks are integral social capital assets for online sellers. While previous research has underscored the positive impact of the follower number on seller performance, little attention has been given to the structure of follower networks and their value implications. This research investigates two structural properties of follower networks—network centralization and density—and examines their main and contingent effects on sellers’ sales performance.Design/methodology/approachA 13-month panel dataset of 1,150 sellers in Etsy, a social marketplace for handmade and vintage products, was collected and analyzed. A fixed effects model was adopted to validate the hypotheses on the main effect of centralization and density, as well as the moderating effects of two store attributes: store age and product diversification.FindingsWe find that both network centralization and density negatively impact sellers’ sales performance, and these effects vary across store age and product diversification levels. Specifically, the negative effect of network centralization is less pronounced for older stores than young ones, whereas the negative effect of density is more severe for stores with high product diversification.Originality/valueThis research contributes to social commerce research by highlighting the significance of network structure, alongside network size, in assessing the value of followers and offers practical guidance for sellers in social marketplaces seeking to optimize their follower networks.

Natural genetic variation and negative density effects in plant-nematode interactions.

Arabidopsis thaliana is a suitable host for phytoparasitic nematodes of the genus Meloidogyne. Successful nematode infection leads to the formation of root galls. We tested for natural genetic variation and inoculation density effects on nematode reproductive success in the interaction between A. thaliana and Meloidogyne javanica. We inoculated different Arabidopsis genotypes with two sources of nematodes at two different doses, using a mild protocol for inoculum preparation. We counted root galls and egg masses 2 months after inoculation. We obtained a high number of successful nematode infections. Infection success differed among Arabidopsis genotypes in interaction with the nematode source. Overall, infection success and reproductive success of nematodes were lower at a higher inoculum dose of nematodes. Our results indicate that natural genetic variation in both host plants and nematodes, as well as short- and long-term negative density effects, shape nematode reproductive success.

Benefits of Best Practice Guidelines in Spine Fusion: Comparable Correction in AIS with Higher Density and Fewer Complications.

There is significant variability in surgeons' instrumentation patterns for adolescent idiopathic scoliosis surgery. Implant density and costs are difficult to correlate with deformity correction, safety, and quality of life measures. Two groups of postoperative adolescents were compared based on exposure to a best practice guidelines program (BPGP) introduced to decrease complications. Hybrid and stainless steel constructs were dropped, and posterior-based osteotomies, screws, and implant density were increased to 66.8 ± 12.03 vs. 57.5 ± 16.7% (p < 0.001). The evaluated outcomes were: initial and final correction, rate of correction loss, complications, OR returns, and SRS-22 scores (minimum two-year follow-up). 34 patients were operated on before BPGP and 48 after. The samples were comparable, with the exceptions of a higher density and longer operative times after BPGP. Initial and final corrections before BPGP were 67.9° ± 22.9 and 64.6° ± 23.7; after BPGP, the corrections were 70.6° ± 17.4 and 66.5° ± 14.9 (sd). A regression analysis did not show a relation between the number of implants and postoperative correction (beta = -0.116, p = 0.307), final correction (beta = -0.065, p = 0.578), or loss of correction (beta= -0.137, p = 0.246). Considering screw constructs only (n = 63), a regression model controlled for flexibility continued to show a slight negative effect of density on initial correction (b = -0.274; p = 0.019). Only with major curve concavity was density relevant in initial correction (b = 0.293; p = 0.038), with significance at 95% not being achieved for final correction despite a similar beta (b = 0.263; p = 0.069). Complications and OR returns dropped from 25.6% to 4.2%. Despite this, no difference was found in SRS-22 (4.30 ± 0.432 vs. 4.42 ± 0.39; sd) or subdomain scores pre- and post-program. Although it appears counterintuitive that higher density, osteotomies, and operative time may lead to fewer complications, the study shows the value of best practice guidelines in spinal fusions. It also shows that a 66% implant density leads to better safety and efficacy, avoiding higher costs.

Density, Temperature, and Comingled Species Affect Fitness within Carrion Communities: Coexistence in Phormia regina and Lucilia sericata (Diptera: Calliphoridae)

Blow fly (Diptera: Calliphoridae) interactions vary between competition and facilitation. Female blow flies engage in aggregated egg-laying, resulting in larval feeding masses differing in density and species composition. Numerous species are abundant within the same season, and some oviposit near or directly on eggs of other species, modifying their oviposition location choice depending on the presence or absence of other species. The ability to coexist on carrion, a temporary resource, was successfully attributed to resource, spatial, and temporal heterogeneity. Despite these broad categorizations, the specific mechanisms of coexistence within blow fly communities require further investigation. This study investigates variation in temperature and larval density as potential mechanisms of coexistence between two forensically important blow fly species: Lucilia sericata Meigen and Phormia regina Meigen (Diptera: Calliphoridae). Larval density, species ratio mix, and ambient temperature during development were manipulated in the presence of conspecifics and heterospecifics in the laboratory, and the fitness of each species was measured. In heterospecific treatments, the survival and body size of P. regina increased even at high ambient temperatures. In contrast, the survival of L. sericata remained unaffected by density or presence of heterospecifics, whereas body size increased in L. sericata-dominated heterospecific treatments depending on temperature and density. The negative effects of density were observed at high ambient temperatures, suggesting that density impacts are a function of ambient temperature. Overall, species coexistence was dependent on temperature, which mediated the outcome of species interactions.

Density effects on native and non‐native trout survival in streams

AbstractEnvironmental stressors associated with a changing climate and non‐native fish, individually, represent significant threats to native fish conservation. These threats can exacerbate risks to native fishes when conditions interact at the trailing edge of a population's distribution. We collected capture–mark–recapture data for Rio Grande cutthroat trout (RGCT, Oncorhynchus clarkii virginalis) at the trailing edge of all cutthroat trout distributions from eight northern New Mexico populations. We used a factorial sampling design from streams characterised as “cool” or “warm” and whether RGCT were sympatric with non‐native brown trout (Salmo trutta). We tested competing hypotheses that warm temperatures, reduced flows, high densities and sympatry with brown trout would negatively impact RGCT apparent survival rates. We found the strongest evidence for a non‐native trout interaction with total trout density affecting RGCT apparent survival rates. Our results are consistent with patterns observed in northern cutthroat trout populations where non‐native salmonids negatively impacted apparent survival rates. We also found that a negative density effect was observed on allopatric RGCT and sympatric brown trout apparent survival, but a positive density effect was observed for sympatric RGCT. These results suggest higher density populations of RGCT may be more resilient to displacement by non‐native trout than low‐density populations.

Some of the Mechanisms for Coexistence of Tree Species Diversity in Tropical Forests: A Review of Effects of Tree Density Dependence

Tree communities contribute to maintenance of species diversity in tropical forests. Coexistence of many tree species is not without competition. Therefore, coexistence of tree species and size diversities occur sequentially or simultaneously in tropical natural forests. Understanding coexistence and competition mechanisms of tree species requires knowledge of interactions within and between species. However, many conservation efforts and strategies failed due to inability to identify and maintain functional coexistence mechanisms among tree species in the forest. Also, most trees died because of pressure on their habitats and not because of limiting growth resources. Hence, species identity, minimum distance and size of the neighbouring trees which are responsible for coexistence of competing trees in most tropical forests have not been explicitly reviewed. Therefore, this review evaluated some of the density dependent mechanisms for coexistence of tree species alpha diversity in tropical forests. Many interactive mechanisms are responsible for coexistence tree species in tropical forests. Inter- and intra-specific competitions are the most significant and both facilitate positive and negative density dependence. Therefore, switching from negative to positive density dependence may occur in some situations. Positive and negative density effects regulate species abundance and coexistence through conspecific and heterospecific structures. Aggregates of conspecific and heterospecific neighbours constitute forest spatial structure. Negative density interactions are mutually exclusive and basically ranged from effect of species identity of neighbours, distance to neighbours and tree size of the neighbours to reference trees in the community structures. Some mechanisms shorten distances for heterospecific than conspecific interactions. Conspecific structures improved survival and growth of rare tree species. Interactive mechanisms in tree community and population structures facilitate species diversity and size inequality, respectively.

A novel geometric parameter to evaluate the effects of block form on solar radiation towards sustainable urban design

The utilization of solar energy plays an important role in coping with global climate change and low-carbon development. Solar radiation in the urban environment is affected by urban block geometry. The relationship between solar radiation and urban block geometry in Nanjing, which has a temperate climate, was studied in this paper. Two hundred generic models in eight typologies that represent a diverse range of urban block density and forms were examined. Seven geometric parameters and three periods of solar radiation on urban blocks, including a year, one typical week in summer, and one typical week in winter, were calculated. Four aspects of solar radiation were investigated at the block scale: (1) the relationship between urban density and solar radiation, (2) the solar radiation on different layout types of urban blocks, (3) the seasonal effect of solar radiation on buildings and open spaces, and (4) the potential of solar photovoltaic technology utilization in block surface. In addition to the obvious negative effect of density, this study indicated that the solar radiation on buildings and surrounding open spaces was significantly influenced by block form. Block surface ratios are the most influential geometric parameters for the solar radiation on buildings, while open spaces are more affected by sky view factor. The seasonal effect on solar radiation presents a much greater impact on open spaces than on buildings. This study highlights the important role that urban geometry plays in the on-site solar energy harvesting.

Determinants of spring molt in bighorn sheep: life-history, plasticity and phenology.

Anthropogenic climate change and habitat alterations increase the importance of understanding the causes and consequences of variation in phenological traits. Although the timing of phenological events may vary in response to both direct and mediated effects, methods to measure and distinguish direct and mediated effects have seldom been used. We used a Bayesian structural equation model (SEM) to evaluate potential direct and mediated effects of intrinsic individual and environmental factors on the timing and progression of spring molt in bighorn sheep. The SEM showed that molt phenology varied across years, was earlier in prime-aged and in heavier individuals, slower in males, and later in lactating ewes, especially if they were light. These results highlight how individual variation in intrinsic traits and life-history leads to substantial variation in a phenological trait. Indirect effects in the SEM predicted a delay in sheep molt phenology at high population density mediated through negative density effects on body mass and lactation probability. Cooler temperatures in late spring were also predicted to delay molt phenology via a negative effect on body mass. Finally, lactation reduced ewe mass which was predicted to delay molt phenology. This mediated effect thus increased the total delay (sum of direct and mediated effects) in molt phenology experience by lactating ewes. Our results underline the importance of estimating direct and indirect effects when modeling phenological traits. Because indirect effects could substantially affect estimates of total plasticity, they should be critically important to accurately predict phenological mismatches and demographic consequences of environmental change.

Positive Effects of Elevated Platforms and Straw Bales on the Welfare of Fast-Growing Broiler Chickens Reared at Two Different Stocking Densities.

Simple SummaryFast-growing broiler chickens commonly experience welfare issues, such as foot and hock lesions or walking difficulties due to their genetics or the barren environment. This study assessed the impacts of elevated platforms and straw bales on the welfare of fast-growing broilers reared at two different stocking densities. The higher stocking density had negative impacts on foot and hock lesions and walking ability, whereas these welfare issues were partly positively affected by enrichments at both stocking densities.In conventional rearing systems, fast-growing broiler chickens commonly experience welfare issues, such as contact dermatitis, walking difficulties or a lack of expression of species-specific behaviours. Enriching their environment may be a way to improve their welfare. The objective of this study was to evaluate the benefits of elevated platforms and straw bales on the welfare of fast-growing broiler chickens reared at two different stocking densities. A total of 14,994 Ross 308 broilers were housed in 12 pens according to 4 treatments: 31 kg/m2 with or without enrichments and 41 kg/m2 with or without enrichments. The broilers’ walking ability, footpad dermatitis (FPD), hock burns (HB), weight, mortality and litter quality were assessed. Stocking density had a negative effect on FPD and HB, whereas enrichments reduced the occurrence of FPD and HB at both densities. There was a positive enrichment effect and a negative density effect on body weight at 25 days and on walking ability, but no effect on the litter quality or mortality rate. These results confirm that an enriched environment improves animal welfare in confined chickens, regardless of the stocking density. Reducing stocking density clearly appears to be an important means of increasing animal welfare.

Cohort strength and body size in co-occurring salmonids in a small stream network: variation in space and time

Trout and salmon commonly coexist in stream networks. Exploring similarities and differences among species can help explain coexistence and invasive ability. Here, we describe spatial distribution, cohort strengths and size-at-age of three co-occurring species in a small stream network. Spatial distributions varied dramatically among species; native brook trout (Salvellinus fontinalis) occupied all stream reaches, naturalized brown trout (Salmo trutta) were found in the mainstem and lower portions of tributaries and fry-stocked Atlantic salmon (Salmo salar) were limited to the mainstem. Size-at-age also differed among species, Atlantic salmon were consistently the smallest, brook trout were intermediate in size and brown trout were the largest. Despite size differences, mean lengths of brook trout and brown trout were highly correlated among years. Cohort strengths varied considerably across years but were also highly correlated for the two trout species, suggesting strong environmental control on cohort strength and a reduced role for species interactions. At low densities, we observed strong negative effects of density on body sizes and weaker effects otherwise. Overall, these results suggest differences in spatial distribution combined with similarities in response to environmental variation contribute to species coexistence in this small steam network.

Increased reproduction under disturbance is responsible for high population growth rate of invasive Centaurea stoebe

To further our understanding of biological invasions, it is important to evaluate hypothesized causal factors facilitating invasions using manipulative field experiments. Disturbance and density are frequently invoked as major factors operating during the process of plant invasions. Soil disturbance by mowing can increase nutrient and light availability while intraspecific competition can reduce potential invader success. Disturbance can therefore reduce the negative effects of density, however the interaction between these effects on invaders have rarely been tested. We studied the combined effect of intraspecific density and soil disturbance on the population dynamics of Centaurea stoebe, an invader in North America. We used an experimental field study of spotted knapweed established in Stony Brook, NY, to parameterize matrix models for four combined disturbance and density treatments. We conducted elasticity analysis to investigate the potential influence of demographic variables on population growth rate. We also used retrospective analysis to identify the actual influence of these variables on the population growth rate of plants in our experimental study. We found higher differences in λ between disturbance treatments compared to between density treatments. LTRE analysis showed that the increased λ of spotted knapweed in response to disturbance was due to substantial increases in survival of vegetative plants and reproduction. Prospective elasticity analysis revealed that λ was most sensitive to small changes in the transition of vegetative plants to reproductive plants, and the production of vegetative plants from reproductive plants. Our results show that the increased growth rate response of spotted knapweed populations to disturbance occurs irrespective of density, and emphasizes the importance of reducing reproduction in the management of spotted knapweed.

The enemy of my enemy: multiple interacting selection pressures lead to unexpected anti-predator responses.

Despite being a major selective force, predation can induce puzzling variability in anti-predator responses-from lack of predator aversion to lifelong predator-induced fear. This variability is hypothesised to result from variation in the trade-offs associated with avoiding predators. But critical information on fitness outcomes of these trade-offs associated with anti-predator behaviours is lacking. We tested this trade-off hypothesis in Aedes aegypti, by examining oviposition site selection decisions in response towards larval predation risk and comprehensively measuring the fitness implications of trade-offs of avoiding larval predators, using three fitness measures: larval survival, development time and size. In a field study, we find that adult females show a surprisingly variable response to predators, ranging from attraction to avoidance. This variation is explained by fitness outcomes of oviposition along a predation-risk gradient that we measured in the laboratory. We show that ovipositing females could gain fitness benefits from ovipositing in pools with a low density of predators, rather than in predator-free pools, as predators provide a release from negative density effects of conspecific larvae that might co-occur in a pool. Interacting selection pressures may thus explain diverse prey responses. We suggest other systems in which similarly unexpected prey behaviour is likely to occur.

Exploring impacts of the built environment on transit travel: Distance, time and mode choice, for urban villages in Shenzhen, China

Context-specific research are necessary to promote public transit by optimizing the built environment in the process of urban renewal. Using data of residential travel survey in Shenzhen, China in 2014, this paper investigated how built environment affected transit travel in urban villages where low-income group resided, and they are all tenants. Structural equations modelling was employed to express the effects of socio-economic, public transit service related and built environment variables on travel mode choice, travel time and distance, with control for residential self-selection. It is found that after considering the self-selection effect, the influence of density and transit availability on travel distance, travel time and transit mode choice in urban villages are still significant. For urban villages, transit availability matters greatest for transit promotion, but the negative effect of density on transit mode choice and none effect of mixed land use are unusual as previous findings. This is partly because of relatively low income, low car ownership, and less elastic travel demand of tenants living in urban villages. Our findings provide some insights into transit-oriented urban renewal that when transforming urban villages, emphasis should be put on enhancement of transit availability, and the mixed land use could be put in the last consideration when there is limited time and funds.

Density-dependent growth in \u2018catch-and-wait\u2019 fisheries has implications for fisheries management and Marine Protected Areas

Stock enhancement activities provide an opportunity to examine density-dependent suppression of population biomass which is a fundamental issue for resource management and design of no-take-zones. We document ‘catch-and-wait’ fisheries enhancement where all but the largest lobsters are thrown back, recapturing them later after they have grown to a larger size. The residency, rate of return, and potential negative density-dependent effects of this activity are described using a combination of tagging and v-notching and by relating spatial growth patterns to population density defined with Catch Per Unit Effort. The results successfully demonstrated the concept of catch-and-wait practices. However, a density-dependent suppression of growth (in body size) was observed in male lobsters. This demonstrates a mechanism to explain differences in lobster sizes previously observed across EU fishing grounds with different stock densities. This negative effect of density could also affect individual biomass production in marine reserve or no-take zones.

Factors affecting population regulation of a colonial vulture

Two hypotheses have been proposed to link population regulation to density‐dependent changes in demographical parameters: the habitat heterogeneity hypothesis (HHH) states that, as population density rises, an increasing proportion of individuals are forced to occupy low‐quality territories, which provokes a decline in average per‐capita survival and/or productivity although some individuals show no decline in fecundity; and the individual adjustment hypothesis (IAH), which suggests that increased densities lead to reductions in survival and/or fecundity by enhancing agonistic interactions, which affect all individuals to a similar extent. However, density‐dependent effects can be affected by density‐independent factors (DIF), such as weather. We test the effects of density dependence on annual reproductive success in Griffon Vultures Gyps fulvus at four spatial scales, nest‐site, cliff, colony and metacolony, in northern Spain from 2008 to 2015. Our results showed most support for the HHH at all scales. At the colony and cliff scale, IAH and DIF had similar importance, whereas there was little evidence of IAH at the metacolony and the nest scale. The best protected eyries (caves, potholes and sheltered ledges) produced the most fledglings and were used preferentially, whereas low‐quality eyries (exposed ledges or open crevices) were used only when the number of breeders increased. The significant interaction between breeding failure and density found for the more exposed eyries suggests that at higher densities, breeding pairs are forced to use poorer nesting areas, and the negative effect of density at the cliff scale could be due to the combined effect of a higher proportion of pairs using low‐quality eyries and the negative effect of rainfall.

The effect of localized density on housing prices in Singapore

This paper measures how localized residential density impacts housing prices in Singapore. Using exogenous variation in residential density, we find that an increase in density causes non-trivial decreases in property values: a 10% increase in density decreases price per square foot by between 1.3% and 2%. To the best of our knowledge, ours is the first paper to measure this effect.Further, we find that the negative effect of density is biggest in magnitude for low density apartment projects and the magnitude is decreasing in the density of the project, and that the negative effect of density is increasing in magnitude in the number of facilities in the project. In contrast, the effect of project density does not differ significantly by either project height or amount of open space.Our results contribute to the discussion on whether a denser urban form is a goal worth pursuing, suggesting that at least part of the benefits arising from externalities of high density are offset by the negative effects of localized density, which is manifested in households' willingness to pay a premium to live in low density apartment projects.

The Effect of Localized Density on Housing Prices in Singapore

This paper measures how localized residential density impacts housing prices in Singapore. Using exogenous variation in residential density, we find that an increase in density causes non-trivial decreases in property values: a 10% increase in density decreases price per square foot by between 1.3% and 2%. To the best of our knowledge, ours is the first paper to measure this effect. Further, we find that the negative effect of density is biggest in magnitude for low density apartment projects and the magnitude is decreasing in the density of the project, and that the negative effect of density is increasing in magnitude in the number of facilities in the project. In contrast, the effect of project density does not differ significantly by either project height or amount of open space. Our results contribute to the discussion on whether a denser urban form is a goal worth pursuing, suggesting that at least part of the benefits arising from externalities of high density are offset by the negative effects of localized density, which is manifested in households' willingness to pay a premium to live in low density apartment projects.

Life history traits influence the strength of distance- and density-dependence at different life stages of two Amazonian palms.

Natural enemies are known to be important in regulating plant populations and contributing to species coexistence (Janzen-Connell effects). The strength of Janzen-Connell effects (both distance- and density-effects) varies across species, but the life history traits that may mediate such a variation are not well understood. This study examined Janzen-Connell effects across the life stages (seed through adult stages) of two sympatric palm species with distinct phenologies and shade tolerances, two traits that may mediate the strength and timing of Janzen-Connell effects. Populations of two common palm species, Attalea phalerata and Astrocaryum murumuru , were studied in Manu National Park, Peru. Seed predation experiments were conducted to assess Janzen-Connell effects at the seed stage. In the post-seed stages, spatial point pattern analyses of the distributions of individuals and biomass were used to infer the strength of distance- and density-effects. Seed predation was both negative distance- and density-dependent consistent with the Janzen-Connell effects. However, only seedling recruitment for asynchronously fruiting Attalea phalerata was depressed near adults while recruitment remained high for synchronously fruiting Astrocaryum murumuru , consistent with weak distance-effects. Negative density-effects were strong in the early stages for shade-intolerant Attalea phalerata but weak or absent in shade-tolerant Astrocaryum murumuru. Distance- and density-effects varied among the life stages of the two palm species in a manner that corresponded to their contrasting phenology and shade tolerance. Generalizing such connections across many species would provide a route to understanding how trait-mediated Janzen-Connell effects scale up to whole communities of species.

Field manipulations of resources mediate the transition from intraspecific competition to facilitation.

Population density affects individual performance, though its effects are often mixed. For sessile species, increases in population density typically reduce performance. Still, cases of positive density-dependence do occur in sessile systems and demand explanation. The stress gradient hypothesis (SGH) predicts that under stressful conditions, positive effects of facilitation may outweigh the negative effects of competition. While some elements of the SGH are well studied, its potential to explain intraspecific facilitation has received little attention. Further, there have been questions regarding whether the SGH holds if the stressor is a resource. Most studies of interactions between the environment and intraspecific facilitation have relied on natural environmental gradients; manipulative studies are much rarer. To test the effects of intraspecific density and resources, we manipulated resource availability over natural population densities for the marine bryozoan Watersipora subtorquata. We found negative effects of density on colony performance in low resource environments, but mainly positive density-dependence in high resource environments. By adding resources, competition effects were reduced and the positive effects of facilitation were revealed. Our results suggest that resource availability mediates the relative strength of competition and facilitation in our system. We also suggest that intraspecific facilitation is more common than may be appreciated and that environmental variation may mediate the balance between negative and positive density-dependence.

Genotypic diversity mitigates negative effects of density on plant performance: a field experiment and life cycle analysis of common evening primrose Oenothera biennis

Summary Genotypic diversity in plant populations is known to enhance plant performance and ecosystem function. Nonetheless, the effect of genotypic diversity has rarely been examined across a population's lifecycle despite the expectation that changing conditions, such as population density, will alter the benefits of diversity. We simultaneously manipulated a component of genotypic diversity (richness, the number of genotypes) and density of common evening primrose Oenothera biennis to address the consequences for herbivory and lifetime fitness in a 2‐year field experiment that spanned seed germination to lifetime fruit production. We genotyped &gt;1100 seedlings with microsatellite DNA markers to determine realized diversity and density in plots sown with O. biennis seeds. Our design achieved quantitative variation in plant density and diversity, with one to 44 individuals established in field plots and two to eight genotypes per polyculture plot (based on microsatellite analysis of reproductive plants). We found a strong interaction between seed density and genetic diversity, with germination and establishment being 24% higher in genetic polycultures than monocultures, but only at low seed density. At high seed density, the opposite pattern emerged, with polycultures having 12% fewer individuals established than monocultures. Initial effects of emergence on plot density persisted through to the fruiting stage. Higher plant densities resulted in increased mortality, decreased probability of reproduction, decreased plant height and lower levels of lifetime fruit production per plant. Increasing genotypic diversity increased the probability of reproduction overall and showed a significant interaction with plant density mitigating the negative effects of high density on individual height and lifetime fruit production. Synthesis. Plant density and genotypic diversity interacted from the very early stages of seed germination and establishment of Oenothera biennis. This effect persisted over the 2‐year life cycle of plants, and genotypic diversity buffered against the negative fitness consequences of high plant density. These results imply a dynamic interplay between the long‐held paradigm of density effects in plant ecology and the genetic structure of populations.